Deltapodus

Mateus, Octávio, Milàn, Jesper, Romano, Michael & Whyte, Martin A., 2011, New Finds of Stegosaur Tracks from the Upper Jurassic Lourinhã Formation, Portugal, Acta Palaeontologica Polonica 56 (3), pp. 651-658 : 651-653

New Deltapodus tracks

Nine, well−preserved Deltapodus pes tracks and two manus tracks were discovered in coastal cliff sections west of Lourinhã ̕ Fig. 1 ). In the following account, the specimens are named after the locality from where they were collected ̕ Table 1). All specimens were found preserved as natural casts and are stored in the collection of the Museum da Lourinhã.

Vale Frades (VF).—The first Deltapodus pes track, discovered in 2003, was preserved as an eroded natural cast of sandstone on a pedestal of clay. The track was found together with a large ornithopod track ̕ Mateus and Milàn 2008). Anatomical details are not preserved, except for the three short blunt toes and a relatively wide square heel ̕ Table 1, Fig. 2A).

Peralta (PN and PS).—A pes track, found north of the beach of Peralta ̕PN), has faint skin striations in the heel area and on the sides of the digits. The heel in this specimen is rounded, tapering to a slightly pointed end ̕ Fig. 2B). Another larger pes track ̕PS) was found in situ in the steep coastal cliffs south of the beach ̕ Table 1, Fig. 2C).

Porto Barcas (PBN and PBS 1–6).—On the north side of Porto Barcas, an asymmetric pes track ̕PBN) was collected. Striations from the skin are preserved on parts of the track walls ( Table 1, Fig. 2D).

Four pes and two manus tracks were found south of the beach of Porto Barcas. The largest pes track (PBS 1) has faint striations from the skin preserved on parts of the trackwalls. The track is slightly deformed sideways as if the animal's foot has been sliding anterolaterally through the sediment ( Fig. 2E).

A slightly smaller specimen (PBS 2) ( Table 1, Fig. 2F) has well−preserved skin impressions covering the plantar surface of the track, as well as striations preserved on the track walls ( Fig. 3 ). The cast reveals a skin texture consisting of closely packed subrounded tubercles 4–8 mm in diameter and one millimetre high. There is no significant difference in size or shape of the “scales” within the plantar surface, although laterally the “scales” are slightly smaller (4–5 mm wide). The tubercles are evenly distributed over all the plantar surface and only the hoof−like distal parts of the digits are smooth ( Fig. 3 ), though some of the detail is obscured by invertebrate burrows that cross the track just behind the digits. The heel of the track is square in outline. Specimen PBS 3 lacks part of the heel and one side, and has only faint striations preserved on the track walls. It appears to have been tapering towards the heel, as in PBN ( Fig. 2G). Another incomplete specimen (PBS 4) lacks parts of two digits. The width of the track decreases posteriorly, giving the track a triangular appearance ( Fig. 2H).

Two natural casts of deeply impressed manus tracks ( PBS 5 and 6) were found associated with the pes tracks. The manus casts are semilunate in shape, without any indications of free digits. One specimen ( PBS 5 ) is eroded and shows no striations from the skin ( Table 1, Fig. 4A ). The other specimen ( PBS 6 ) is widest at the bottom, suggesting the soft sediment of the track walls partly converged after withdrawal of the foot ( Table 1, Fig. 4B 1 , B 2). The front of the manus is smooth, without indications of individual digits, and striations from the skin being dragged through the substrate can be traced from top to bottom of the cast ( Fig. 4B 3 ) .

Porto Dinheiro (PD).—A probable left pes (PD) was associated with theropod tracks of varying sizes and large sauropod tracks ( Mateus and Milàn 2010). Faint striations from the skin are preserved on the sides of the cast, and the shape of the heel is square ( Fig. 2I).

VF PN PBN PBS 1

PS PBS 2 cm 50

PBS 3 PBS 4 PD

Figures

Fig. 1. Location map. The eleven new specimens of Deltapodus were found along the coast west of the town Lourinhã, in the central−west of Portugal. Each specimen has been given an abbreviation corresponding to the locality where it was found.

Fig. 3. Deltapodus track PBS 2 (ML 1347) from the Lourinhã Formation (Upper Jurassic, Portugal). A. Plantar view. B. Detail of scaly skin impressions. C. Vertical striations of the skin on the cast surface.

Fig. 4. The two associated natural casts of Deltapodus manus tracks found at Porto Barcas, Lourinhã Formation (Upper Jurassic, Portugal). Both tracks show a pronounced semilunate shape. A. Manus track PBS 5 (ML 1351) seen from below. B. Manus track PBS6 (ML 1352) seen from below (B1), caudal view (B2), and enlarged section of the front (B3), showing the vertical striations covering the front and sides of the cast.